In March 2019, a tropical cyclone in the south-west Indian Ocean caused widespread flooding in a number of countries. The flooding and the damage caused by the cyclone meant that many people were at serious risk of cholera. After the natural disaster occurred, many different areas reported outbreaks of cholera. Within a short time the disease had spread widely and large numbers of people were affected.

Mark scheme

Marking points from the official mark scheme (Feb/Mar 2021). The mark or mark type is shown in brackets.

1. [1] 6(a) Vibrio cholerae ;
2. [3] 6(b) any three from: 1 cholera already, endemic / present, in area; 2 contaminated water / water contains pathogen ; R polluted water 3 pathogen transmitted by, faecal-oral route / AW ; 4 ref. to changed living conditions ; e.g. no piped, treated, drinking water / disruption to water treatment plants no safe disposal of sewage / disruption to sewage treatment plants 5 ref. to inability to practise good hygiene ; e.g. washing (utensils) in contaminated water not able to wash hands after defaecation latrines not covered 6 AVP; e.g. ref. to flies transferring pathogen from, uncovered latrines / (contaminated) faeces
3. [3] 6(c)(i) any three from: 1 mRNA unable to bind ; 2 ribosome subunits unable to come together; 3 tRNA unable to, enter / bind to, ribosomes ; 4 mRNA codon-tRNA anticodon binding prevented ; 5 translation, prevented / does not begin or polypeptide synthesis prevented / polypeptides not synthesised ; A protein for polypeptide 6 enzymes required for growth not produced / example of role of protein in growth e.g. for membrane formation ;
4. [1] 6(c)(ii) cell wall;
5. [4] 6(d) any four from: vaccination programme to max 3: 1 vaccines stimulate (active) immunity to cholera / AW; 2 idea that if infected with, pathogen / V. cholerae, people do not become ill with cholera or the immune system destroys pathogen before it can, cause harm / spread ; 3 ref. to herd immunity ; A described e.g. enough people effectively immunised to prevent spread idea that unvaccinated people surrounded by immunised people 4 AVP; e.g. idea that reduces reservoir of pathogen in population treatment to max 3: 5 (oral / intravenous) rehydration therapy, decreases recovery time / cures more quickly; 6 (more likely that) contaminated faeces disposed of safely / decreased risk of spread via contaminated faeces 7 more able to practise good hygiene ; 8 time spent in medical centre acts as quarantine / infected people not in general population; 9 (so) decreases, density / proportion, of infected people to reduce risk of spread ; 10 AVP; e.g. medical centres able to monitor antibiotic use and provide most effective medication medical centres, accessible to many parts of the country / widespread idea that medical centres mean people treated sooner decreasing time when people are infectious injecting antibodies